new Promise((resolve, reject) => {
    setTimeout(() => resolve('hello'), 10);
}).then(value => {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve(value + 'lagou', 10));
    });
}).then(value => {
    return new Promise((resolve, reject) => {
        setTimeout(() => resolve(value + 'I love U', 10));
    });
}).then(value => console.log(value));